Characteristic equation of a hybrid (PV-T) active solar still Original Research Article

A hybrid (PV-T) active solar still is a combination of solar still and flat plate collector (FPC) integrated with glass–glass photovoltaic module. In this paper, two analytical methods are used to establish characteristic equation of hybrid (PV-T) active solar still based on annual experimental observations. In method-1, linear and non-linear curves are plotted for instantaneous gain efficiency (ηi) with respect to x = (Tw − Ta) / I(t) which is a representative factor of climatic and operational parameter. In method-2, a characteristic equation for solar still similar to FPC i.e. ηi = A + B ∙ {(Tw − Ta) / I(t)} + C ∙ {(Tw − Ta)2 / I(t)} has been found using a matrix method. Further, both the methods are used for estimation of instantaneous loss efficiency (ηiL). All these equations are established by assuming steady state condition for thermal testing of solar still. The comparative performance of these two methods has also been estimated in terms of root mean square percentage (RMS) error. It has been observed that the performance of non-linear characteristic equation is better than linear characteristic equation.